AVS 52nd International Symposium
    Surface Science Friday Sessions
       Session SS1-FrM

Paper SS1-FrM5
157 nm Laser Interactions with Fused Silica@footnote 1@

Friday, November 4, 2005, 9:40 am, Room 202

Session: Surface Modification through Etching
Presenter: S.R. John, Washington State University
Authors: S.R. John, Washington State University
J.A. Leraas, Washington State University
S.C. Langford, Washington State University
J.T. Dickinson, Washington State University
Correspondent: Click to Email
The F@sub 2@ excimer laser, with a wavelength of 157 nm and a photon energy of 7.8 eV, has been shown useful for micromachining a number of technologically useful materials and has potential applications in developing optics, resists, and scanners for DUV lithography. Two materials that have been examined extensively are fused silica and PTFE (Teflon). Little has been done to understand the detailed mechanisms underlying the superior etching behavior of these materials at 157 nm. Here we present a summary of our initial studies. Beginning at fluences well below threshold for plasma formation, we have examined the direct desorption of atomic ions from fused silica surfaces at 157 nm. We used time resolved mass spectroscopy to identify the species and determine their kinetic energies. Both Si@super +@ and O@super +@ are observed. Prolonged irradiation reduces the emission intensities, consistent with the consumption of defects by the emission process. Molecular dynamics simulations of the silica surface suggest that silicon ions bound at surface oxygen vacancies (analogous to E' centers) provide suitable configurations for emission. Direct emission involving antibonding chemical forces (Menzel-Gomer-Redhead model) are suggested as the origin of the observed kinetic energies. If time permits, results on PTFE will be presented, showing significant neutral and ion emissions (with high kinetic energies). @FootnoteText@ @footnote 1@This work was supported by the Department of Energy.